1. Field of Invention
The present invention relates generally to a projector having a lamp assembly that allows the user to replace the projection lamp easily and economically. More specifically, the present invention describes a liquid crystal display ("LCD") projector including a pivoting easy-access self-aligning projection lamp assembly that employs cost-efficient metal halide bulbs. The lamp assembly of the present invention includes unidirectional and pre-aligned lamp sockets that automatically align and orient the lamp in the correct optical position within the projector.
2. Description of the Prior Art
Various types of projectors, such as overhead and LCD projectors, are known in the prior art. Generally, these projectors include a lamp, that is, a light source such as an incandescent or quartz bulb, that enables the projection of images onto a screen. The term lamps also includes lasers and halogen, metal halide, and fluorescent bulbs, as well as other sources of light known in the art.
Projectors typically include relatively complex optical projection systems that direct and focus the light from the lamp. Careful alignment and orientation of the lamp within the optical projection system is very important to obtaining bright and well-defined projected images.
Traditionally, projection lamps have been specifically designed for a projector and have been very costly components. Lamp replacement usually was awkward, requiring a technician to dismantle part of the projector housing and to reach into the projector housing and carefully manipulate the glass bulb to ensure proper alignment. The dependence on securing a technician and a replacement bulb limited the reliability of projectors for out-of-town and portable presentations.
Attempts have been made to design projector systems that allow for the replacement of lamps by the user. To eliminate the need to disassemble part of the projector to gain access to the lamp, some designs have included replacement lamps already housed within the projector housing. For example, one design included rotary plates having a plurality of arc tubes and blocks. By rotating a set of cams, an old burnt arc tube was separated from the lamp and a new arc tube was replaced as the light source. Nevertheless, in internal replacement systems the replacement bulbs and the replacement mechanism occupy significant space inside of the projector body, a problem when designing compact or portable projectors. Furthermore, internal replacement systems eventually exhaust the internal supply of bulbs, again necessitating the dismantling of the projector before new bulbs may be installed.
Other designs have attempted to simplify lamp replacement by utilizing different variations of a connectorized lamp cartridge. A lamp is potted and factory aligned within a cartridge that includes cables, connectors and reflectors. The cartridge is accessed by removing an access panel and pulling out the entire cartridge. The old cartridge is discarded and an entire new cartridge is positioned inside of the projector unit. The cartridge replacement system offers relative ease of use and the advantage of having the lamp pre-aligned in optimal position with respect to the reflector and the entire optical projection system. However, replacement of the entire cartridge usually is expensive. In accessing and replacing the cartridge in some designs, the user is given access to the interior regions of the projector housing, which increases the danger of electrical shock or of damage to the precise components of the projector.
Other designs have discussed the use of cartridges including replaceable plug-in halogen lamps. However, halogen lamps lack the luminous efficacy of metal halide lamps. The entire cartridge still has to be removed from and inserted into the projector body. Cartridge replacement systems include a number of loose parts which may be misplaced by the user.
The need remains for a projector that allows for easy access and replacement of a projector lamp. An advantageous design would be user intuitive and would not require special training or tools to replace and align the lamp. In addition, a preferred design would allow the use of brighter metal halide lamps.